This invention relates generally to a leveling device of the type using a flexible transparent hose or tube substantially filled with water or colored antifreeze solution, of the type commonly used in basic construction work and employing the principle of liquid seeking its own level, to establish two or more separate points at an identical level or vertical height. This invention relates more specifically to the provision, in combination with a flexible transparent tubular liquid level, of a liquid control assembly at each end of the tube which is adapted to automatically prevent inadvertent leakage of liquid from the tube and nevertheless permit ease of use of the entire assembly as a leveling device.
In initiating any type of structural work, whether it be a building foundation, installation of a swimming pool, pipe fitting, or ceiling installation, a primary operation is to establish true level or extend a level line between a first and second point. It is common procedure to do this by establishing a first point or mark on, for example, a stake or batter board and then to locate a second point or mark at some distance away from the first mark. This is accomplished by utilizing an elongated relatively small-diameter flexible tube, usually clear plastic, having both ends open to the atmosphere and having the tube substantially filled with liquid. One end of the tube is placed in vertical orientation across the first mark and held in that position while the second end of the tube is vertically oriented at the anticipated general location of the second mark and is adjusted vertically until the end of the liquid column at the first end of the tube is perfectly aligned with the first mark. Then, the end of the liquid column at the second end of the tube establishes the location of the second mark which is accurately level with the first mark.
There are variations of the basic tubular liquid leveling device, one of which includes a reservoir at one end of the tube which can be placed centrally and stationary within the intended area of construction. Then, a plurality of successive marks can be placed outwardly from the reservoir, in registration with the end of the liquid column in the outer end of the tube, and all marks so placed will be level with each other.
In utilizing the known common liquid leveling devices it is necessary to have a removable plug in the tube end which is removed during the leveling operation and then replaced to prevent leakage of the liquid from the tube when the tube end is dropped to the ground or the tube is stored for later use. In the simplest non-reservoir version of the liquid leveling device heretofore described, it is necessary to utilize a plug at each end of the tube, and such plugs are often lost or inadvertently dislodged.